1. Field of the Invention
The invention relates to a pump nozzle for diesel engine, in which an injection pump element comprising a pump piston driven by a cam-shaft and a bushing is combined with an injection nozzle to provide with a unit to be associated to one motor cylinder. The pump piston is surrounded by a control sleeve which is adjustable by an adjusting force in direction of the axis of the pump piston in dependence on operating parameters of the motor for the purpose of varying the beginning of the injection. The pump piston can be rotated relative to the control sleeve for the purpose of adjusting the supplied fuel amount. The control sleeve or a part connected therewith is guided in a manner preventing rotation relative to the pump element body. Such a control sleeve has, as a rule, a control edge located within a plane extending normal to the pump axis and controlling the beginning of fuel injection. An obliquely extending control edge of the control sleeve or of the pump piston defines the end of injection and thus the injected amount of fuel in dependence on the rotated position of the pump piston relative to the control sleeve. By adjusting the height position of the control sleeve, the control edge defining the beginning of injection is earlier or later slid past the control bore of the piston, so that the beginning of supply by the injection pump is adjusted.
2. Description of the Prior Art
From DE-OS 31 43 073, there has become known a pump nozzle of the type in which the control sleeve is axially adjustable for the purpose of adjusting the beginning of injection. In this case, adjusting of the control sleeve is directly effected by means of a hydraulic piston. On account of adjusting the control sleeve directly by means of the hydraulic piston, the adjusting path of the control sleeve is equal to the adjusting path of the hydraulic piston. On account of the adjusting path of the control sleeve being small, there are at disposal only small adjusting paths of the hydraulic piston for adjusting the control sleeve, so that such a control is not delicately sensitive and precise. In an embodiment according to the mentioned DE-OS, the hydraulic piston is connected with the control sleeve via a linkage. Adjusting of the control sleeve becomes inprecise also on account of the play within the linkage. The control sleeve is immediately guided on the pump piston, so that wear is promoted between control sleeve and pump piston. The control piston is guided on the pump piston over a comparatively small guide length, so that there exists the risk for the control sleeve to become jammed on the pump piston, thereby increasing the wear of pump piston and control sleeve and reducing the precision of control. In another embodiment, the axially adjustable hydraulic piston surrounds the pump piston and is itself designed as the control sleeve. Also in this embodiment, the adjusting path of the hydraulic piston is thus equal to the adjusting path of the control sleeve, and there are additionally required sealings which equally detract from the precision and the sensitiveness of the control on account of the friction phenomenon.